Basic Science and ModelingofSolar Energy.ppt

1、Basic Science and Modeling of Solar Energy,by Jeremy Parra and Sandrio Elim,Topics:,Science of Solar Energy Technology Using Solar Energy,Science of Solar Energy,Resources: Energy Flows: Chemistry and Physics background:,“The pp-chain (proton-proton chain) involves a series of nuclear reactions that

2、 are responsible for the generation of energy in the sun. The basis for the suns energy is that four hydrogen atoms fuse to form one helium atom whose mass is slightly less than the mass of the combined four hydrogen atoms. The missing mass is what was converted to energy. “In the pp-chain, two prot

3、ons (moving at very fast velocities) fuse together to create deuterium. A neutrino and a positron are expelled in the process. Deuterium (one proton and one neutron) fuse with one more proton creating Helium-3. A photon is released in this process and this is what gives the sun its energy. After Hel

4、ium-3 is created, it fuses with another of its type and 2 hydrogen atoms are expelled. The result is one atom of Helium-4 and 2 atoms of Hydrogen to start the process all over again. Even though the photons are accountable for most of the suns energy, about 5% of the energy is given off in neutrinos

5、.”-bib. 1,Fig. 1 (copied ,bib.1),Solar fusion,Hydrogen(one proton),electron,Hydrogen,2,Deuterium(one proton one neutron),electron,positron,neutrino,Deuterium,Helium(two protons one neutron),3,photon,Helium,Yield,Sun Light,Photon,If when a photon strikes an electron it has the amount of energy to bre

6、ak the electron-electron bond( band gap) a free electron will result. This results in a positive “hole” and a negative electron.,Hole,Free electron,Photon,Semiconductors,A semiconductor has electrical conductivity greater that insulators but less than good conductors. Silicon has four valence electr

7、ons.Pure silicon is in a perfect state of valence(has no free electrons).,Si,electrons,hole,Free electron,Silicon,nucleus,Semiconductors,When phosphorous is substituted for a silicon atom, there is one electron left The remaining electron is very loosely bound by the slightly more positive charge of

8、 the nucleus of the phosphorous atom. This electron travels easily around the phosphorous atom. Silicon that contains a large number of atoms with an extra valence electron is called n type silicon (n is for negative).,Si,Si,Extra Electron,N-Type,Semiconductors,If a boron atom is substituted for a s

9、ilicon atom, there is one valence electron which has no partner. This missing electron is a hole. This yields a positive charge (the absence of an negative electron). This is a p-type,Hole,P-Type,The binding force of electron pairs is much stronger than the electromagnetic force between an electron

10、and the nucleusThe extra electron moves from the n-type to the p-type And these electrons form valence pairs with the electrons that were missing a pair This results in a shift in charge that creates an electric field in the material. Now the n-side(doped with phosphorus) gains a positive charge. Wh

11、en the electron moved it left a proton “Similarly, the boron atom is surrounded by one more electron than there are positive protons in the boron nucleus.”,Electric Field,The n-type side doped with Phosphorus easily lends its free electron to the positive side (doped with boron). This leaves the n-t

12、ype with one more proton than electron giving the n-type a positive charge. And the p-type now has one more electron the proton yielding a negative charge. This creates an electric field. With out this electric field the freed electron(freed by a photon) would just return to the same hole. But becau

13、se of the electric field the freed electron will move from the negative area to the positive area creating an electric current. And the holes will move in the other direction.,Technology Using Solar Energy,Types of cells: Crystalline Silicona. Single crystalb. Multi-crystallinec. Ribbond. Film Thin

14、films materialsa. Amorphous Siliconb. Cadmium Telluridec. Copper Indium Diselenide 3. Concentrators Components: PV DC-AC Converter Backup Power Generator Stabilizer Electrical Panel,Source:DOE/GO-10097-377 FS 231 - March 1997,Types of PV Cells,Monocrystalline Silicon Cells Multicrystalline Silicone

15、Cells Thick-film Silicon Amorphous Silicon Other thin films: Cadmium telluride Copper indium diselenide Gallium arsenide Tandem cells,1. Monocrystalline Silicon,Most efficient PV tech Complicated process High Cost to manufacture,2. Multicrystalline Silicon,Cheaper Simpler process Less efficiency Gra

16、nular texture,3. Thick-film Silicon,Continuous process Fine grained Bounded to aluminum frame,4. Amorphous Silicon,A thin homogenous layer More effective in absorbing lights Also known as thin film PV Efficiency about 6%,5. Other Thin Films,a. Cadmium telluride and Copper indium diselenide Still in

17、research Very inexpensive process Expected efficiency quite high b. Gallium arsenide High efficiency Relatively temperature independent For special purpose only c. Tandem cells Made of two different cells Usually from silicon and gallium arsenide Better use of incoming light,Manufacturing,How It Wor

18、ks,Math Modeling,1. Optimal Conditionsa. Equationsb. Independent Variables2. Method of Data Collectiona. Softwareb. Units,Bibliography,1) http:/cosmos.colorado.edu/hairgrov/Suns_Energy_Generation 2) http:/www.wikipedia.org/wiki/Deuterium 3) http:/pearl1.lanl.gov/periodic/elements/1.html http:/www.nobel.se/chemistry/laureates/2000/public.html http:/www.scolar.org.uk/html/pdf-page.html http:/sol.crest.org/renewables/re-kiosk/solar/pv/theory/index.shtml http:/www.fsec.ucf.edu/pvt/pvbasics/ http:/www.ips- http:/acre.murdoch.edu.au/refiles/pv/text.html,